Alcohol production method by reducing ester or lactone with hydrogen

ABSTRACT

Provided is an alcohol production method comprising the step of reducing an ester or a lactone with hydrogen to produce a corresponding alcohol without addition of a base compound by using, as a catalyst, a ruthenium complex represented by the following general formula (1):
 
RuH(X)(L 1 )(L 2 ) n   (1)
 
wherein
         X represents a monovalent anionic ligand,   L 1  represents a tetradentate ligand having at least one coordinating phosphino group and at least one coordinating amino group or a bidentate aminophosphine ligand having one coordinating phosphino group and one coordinating amino group, and   L 2  represents a bidentate aminophosphine ligand having one coordinating phosphino group and one coordinating amino group, provided that   n is 0 when L 1  is the tetradentate ligand, and n is 1 when L 1  is the bidentate aminophosphine ligand.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/553,544 (now allowed) filed on Sep. 3, 2009 which claims priorityfrom Japanese Patent Application No. 2008-230916 filed on Sep. 9, 2008and Japanese Patent Application No. 2009-167704 filed on Jul. 16, 2009,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an alcohol production method byreducing an ester or a lactone with hydrogen.

2. Brief Description of the Related Art

Methods for obtaining alcohols by reducing esters and lactones areimportant in chemical synthesis. For obtaining such reactions, thefollowing methods have been proposed: a method in which a stoichiometricamount or more of a metal hydride compound such as silyl hydride, sodiumborohydride and lithium aluminium hydride is used; and a method in whichcatalytic hydrogenation reduction is conducted using molecular hydrogen.The former method has problems including: a great amount of wastegenerated from a reducing agent; and a safety concern raised by the useof a highly-reactive reducing agent. For this reason, recently, thelatter method which is an environmentally friendly technology has beenmore actively developed and examined, regardless of heterogeneous andhomogeneous reductions.

For example, Japanese Unexamined Patent Application Publication No. Sho51-8203 and Org. React., 1954, 8, 1 propose examples of theheterogeneous hydrogenation reduction. However, such proposals have aproblem that a high temperature condition or a high pressure condition,or both of the conditions are needed for the reduction, and otherproblems. Meanwhile, Adv. Synth. Cat., 2001, 343, 802 describes aproduction method under such a condition that racemization of anoptically active ester may not be involved. However, the productionmethod has a problem that, when the ester serving as the substrate hasan aromatic ring, side-reactions frequently occur to produce, forexample, alcohols with the aromatic ring reduced, thus exhibiting a lowselectivity. Moreover, the production method has a disadvantage in termsof cost that a large amount of very expensive catalysts have to be used.Accordingly, the method is difficult to industrially put into practicaluse.

As for the homogeneous reduction, the utilization of a ruthenium complexincluding a phosphine ligand has been proposed in many documents.

For example, J. Am. Chem. Soc. 1981, 103, 7536, Chem. Commun. 1998,1367, and J. Mol. Catal. A: Chem., 2003, 206, 185 disclose methods inwhich monophosphine, diphosphine, triphosphine and tetraphosphineligands, and the like are used. Particularly when a tridentatetriphosphine ligand is used, a relatively high hydrogenation activity isdemonstrated. However, when an ester is not activated for a reduction, afluorinated compound having a large environmental load has to be used asa solvent. This kind of problem makes the methods difficult toindustrially put into practical use. Angew. Chem. Int. Ed. 2006, 45,1113 and Organomet. 2007, 26, 16 disclose hydrogenation reduction ofesters with a ruthenium complex including a tridentate diaminophosphineor aminodiphosphine ligand. In the method of Angew. Chem. Int. Ed. 2006,45, 1113, carbon tetrachloride used when a ligand and a complex areprepared is environmentally harmful, and its production is banned inmost of the world. Moreover, the reaction needs to be conducted at a lowtemperature. Accordingly, the method has a lot of industrialdisadvantages. The method disclosed in Organomet. 2007, 26, 16 hasdifficulties that: a complex is prepared while being irradiated withmicrowaves; the hydrogenation of esters needs to be conducted at a hightemperature of 140 to 150° C.; high yield is obtained only when estersare fluorinated because of the activation for a reduction; and so forth.WO2006/106483, WO2006/106484, WO2008/065588 and Angew. Chem. Int. Ed.2007, 46, 7473 disclose efficient ester hydrogenation reduction methodsusing a ruthenium catalyst including bidentate and tetradentateaminophosphine and iminophosphine as ligands. In the methods, it isnecessary to use an alkali metal alkoxide as a base when the reaction isconducted. Thus, the methods have a problem that the decomposition ofthe compound or racemization occurs in reducing a substrate having abase-labile functional group or reducing an ester having asymmetriccarbon. Meanwhile, J. Am. Chem. Soc. 2005, 127, 516, Japanese PatentApplication Publication No. 2003-104993 and other documents describe aruthenium complex including an aminophosphine or a diphosphine and adiamine as ligands. Such a ruthenium complex is reported to reduce acarbonyl group without adding a base. However, the ruthenium complexreduces only a ketone, and has difficulty in reducing an ester groupthat is present together with the ketone. Meanwhile, complexes as usedin the present invention have been prepared by a multi-stage method asdisclosed in, for example, Organomet. 2004, 23, 6239 and Organomet.2007, 26, 5940. Specifically, in the method: an iminophosphine ligand isreduced in advance; a complex is prepared from the ligand and aruthenium precursor; thereafter the complex is further reduced.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide an alcoholproduction method from an ester or a lactone at high yield and at highcatalytic efficiency under relatively moderate conditions while sidereactions and the like are suppressed, by using a complex and a ligandwhich can be prepared relatively easily. Further, the method forproducing an alcohol is industrially efficient since the complex isprepared relatively easily.

As a result of intensive studies conducted taking the above-describedproblems into consideration, the present inventors have discovered thatit is possible to produce alcohols from esters or lactones at high yieldand at high catalytic efficiency without adding a base compound whileside-reactions and the like are suppressed, by using, as a catalyst, aruthenium complex including a tetradentate ligand, which has at leastone coordinating phosphino group and at least one coordinating aminogroup, or two bidentate aminophosphine ligands, which have onecoordinating phosphino group and one coordinating amino group. Thus, thepresent invention has been achieved.

More specifically, the present invention relates to the followingaspects [1] to [9].

[1] An alcohol production method including the step of reducing an esteror a lactone with hydrogen to produce a corresponding alcohol withoutaddition of a base compound by using, as a catalyst, a ruthenium complexrepresented by the following general formula (1):RuH(X)(L¹)(L²)_(n)  (1)wherein X represents a monovalent anionic ligand, L¹ represents atetradentate ligand having at least one coordinating phosphino group andat least one coordinating amino group or a bidentate aminophosphineligand having one coordinating phosphino group and one coordinatingamino group, and L² represents a bidentate aminophosphine ligand havingone coordinating phosphino group and one coordinating amino group,provided that n is 0 when L¹ is the tetradentate ligand, and n is 1 whenL¹ is the bidentate aminophosphine ligand.

[2] The production method described in [1], wherein X in the complexrepresented by the general formula (1) is BH₄.

[3] The production method described in [1] or [2], wherein thetetradentate ligand represented by L¹ in the complex represented by thegeneral formula (1) further has one coordinating phosphorus atom and onecoordinating nitrogen atom.

[4] The production method described in [3], wherein L¹ in the complexrepresented by the general formula (1) is a tetradentate ligandrepresented by the following general formula (2):

wherein R¹, R², R³, R⁴, R⁵ and R⁶, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aralkyl group which may have a substituent, an aryl group which mayhave a substituent, or a cycloalkyl group which may have a substituent,R¹ and another R¹, R¹ and either R², R³ or R⁴, R³ and R⁴, or R⁵ and R⁶may bond to each other to form a ring, and Q¹ and Q², which may be sameor different, each represent a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond.

[5] The production method described in [1] or [2], wherein L¹ and L² inthe complex represented by the general formula (1), which may be same ordifferent, each represent a bidentate aminophosphine ligand representedby the following general formula (3):

wherein R⁷, R⁸, R⁹, R¹⁰ and R¹¹, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, an aralkyl group which mayhave a substituent, or a cycloalkyl group which may have a substituent,R⁷ and R⁸ or R⁹, R⁸ and R⁹, or R¹⁰ and R¹¹ may bond to each other toform a ring, and Q³ represents a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond.

[6] The production method described in [4], wherein the complex isobtained by reducing a ruthenium complex including a tetradentate ligandrepresented by the following general formula (4) or (5):

wherein R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹, which maybe same or different, each represent a hydrogen atom, an alkyl groupwhich may have a substituent, an aryl group which may have asubstituent, an aralkyl group which may have a substituent, or acycloalkyl group which may have a substituent, R¹² and another R¹², R¹²and R¹³ or R¹⁴, R¹³ and R¹⁴R¹⁵, and R¹⁶, R¹⁷ and another R¹⁷, R¹⁹ andR¹⁷ or R¹⁸, or R²⁰ and R²¹ may bond to each other to form a ring, andQ⁴, Q⁵, Q⁶ and Q⁷, which may be same or different, each represent adivalent arylene group which may have a substituent, an alkylene groupwhich may have a substituent, or a bond, the ruthenium complex beingrepresented by a general formula (6):[Ru(X¹)_(k)(X²)_(l)(Y¹)_(m)(Y²)_(o)(L^(1′))](Z)_(q)  (6)wherein X¹ and X² each independently represent a monovalent anionicligand, Y¹ and Y² each independently represent a neutral monodentateligand, Z represents a monovalent anion that does not coordinate to ametal, and L^(1′) represents the tetradentate ligand represented by thegeneral formula (4) or (5), provided that k, l, m and o are each anatural number between 0 to 2 inclusive, and satisfy 0≦k+l+m+o≦2, and qis 0 when k+l=2, q is 1 when k+l=1, and q is 2 when k+l=0.

[7] The production method described in [5], wherein which the complex isobtained by reducing a ruthenium complex including a bidentateaminophosphine ligand represented by the following general formulae (7a)or (7b):

wherein R²², R²³, R²⁴, R²⁵, R¹⁰⁰, R¹⁰¹, R¹⁰², R¹⁰³, R¹⁰⁴, and R¹⁰⁵,which may be same or different, each represent a hydrogen atom, an alkylgroup which may have a substituent, an aryl group which may have asubstituent, an aralkyl group which may have a substituent, or acycloalkyl group which may have a substituent, R²² and R²³, R²⁴ and R²⁵,or R¹⁰⁴ and R¹⁰⁵ may bond to each other to form a ring, and Q^(7a) andQ^(7b) each represent a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond,the ruthenium complex being represented by a general formula (6′):[Ru(X³)_(k′)(X⁴)_(l′)(Y³)_(m′)(Y⁴)_(o′)(L^(1″))(L^(2″))](Z′)_(q′,)  (6′)wherein X³ and X⁴ each independently represent a monovalent anionicligand, Y³ and Y⁴ each independently represent a neutral monodentateligand, Z′ represents a monovalent anion that does not coordinate to ametal, and L^(1″)and L^(2″), which may be same or different, eachrepresent the bidentate aminophosphine ligand represented by the generalformula (7a) or (7b), provided that k′, l′, m′ and o′ are each a naturalnumber between 0 to 2 inclusive, and satisfy 0≦k′+l′+m′+o′≦2, and q′ is0 when k′+l′=2, q′ is 1 when k′+l′=1, and q′ is 2 when k′+l′=0.

[8] The production method described in any one of [1] to [7], whereinthe prepared complex is used as the catalyst without being isolated froma complex preparing solution.

[9] The production method described in any one of [1] to [8], in whichthe ester or the lactone is an optically active substance, and theobtained alcohol holds an optical purity of 90% or more of that of theester or lactone reduced with hydrogen.

The production method of the present invention enables alcohols to beproduced from an ester and a lactone at high yield and at high catalyticefficiency under relatively low hydrogen pressure and reactiontemperature which are industrially advantageous. In addition, even whenthe ester or the lactone to be reduced is labile to a base, the esterand the lactone can be reduced to alcohols without unnecessary chemicalconversion such as decomposition and polymerization. Moreover, even whenthe ester or the lactone is an optically active substance, the ester andthe lactone can be reduced to alcohols without lowering the opticalpurity. Furthermore, since a catalyst can be prepared easily, the methodof the present invention is industrially advantageous.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, the present invention will be described in detail.

In the present invention, an ester or a lactone is used as a material ofa hydrogenation substrate. Examples of the ester used as thehydrogenation substrate include aliphatic carboxylic acid esters andaromatic carboxylic acid esters. The ester may derive frommonocarboxylic acids or polycarboxylic acids. These esters and lactonesmay have any substituent as long as the substituent does not adverselyaffect the hydrogenation process of the present invention.

In the present invention, examples of the esters used as thehydrogenation substrate include alkyl esters, aryl esters, aralkylesters, cycloalkyl esters, and the like of aliphatic carboxylic acids oraromatic carboxylic acids as follows.

Examples of the aliphatic carboxylic acids include: mono- andpolycarboxylic acids having a linear or cyclic aliphatic group with 2 to50 carbon atoms, preferably 2 to 20 carbon atoms, and more preferably 2to 14 carbon atoms; and mono- and polycarboxylic acids having a 3- to8-membered (preferably, O-5 to 6-membered) monocyclic, polycyclic, orcondensed aliphatic heterocyclic group with 2 to 14 carbon atoms and atleast one heteroatom (preferably 1 to 3 heteroatoms) such as a nitrogenatom, an oxygen atom and/or a sulfur atom. Specific examples thereofinclude acetic acid, propionic acid, butyric acid, valeric acid,hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoicacid, dodecanoic acid, lauric acid, myristic acid, palmitic acid,stearic acid, oleic acid, oxalic acid, propanedicarboxylic acid,butanedicarboxylic acid, hexanedicarboxylic acid, sebacic acid, acrylicacid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid,cyclopentenecarboxylic acid, cyclohexenecarboxylic acid,2-azetidinecarboxylic acid, 2-pyrrolidinecarboxylic acid (proline),3-pyrrolidinecarboxylic acid, 2-piperidinecarboxylic acid,3-piperidinecarboxylic acid, 4-piperidinecarboxylic acid, andpiperazine-2-carboxylic acid.

These aliphatic carboxylic acids may have a substituent. Examples of thesubstituent include an alkyl group, an aryl group, an aralkyl group, acycloalkyl group, an alkoxy group, an aryloxy group, an aralkyloxygroup, a halogen atom, a heterocyclic group, an optionally-protectedamino group, and an optionally-protected hydroxy group.

An example of the alkyl group as the substituent in the aliphaticcarboxylic acids is a linear or branched alkyl group with 1 to 50 carbonatoms, preferably 1 to 20 carbon atoms, and more preferably 1 to 10carbon atoms. Specific examples thereof include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, ann-hexyl group, and an n-octyl group.

An example of the aryl group as the substituent in the aliphaticcarboxylic acids is a monocyclic, polycyclic, or condensed aryl groupwith 6 to 36 carbon atoms, preferably 6 to 18 carbon atoms, and morepreferably 6 to 14 carbon atoms. Specific examples thereof include aphenyl group, a naphthyl group, an anthryl group, a phenanthryl group,and a biphenyl group.

An example of the aralkyl group as the substituent in the aliphaticcarboxylic acids is a group in which at least one hydrogen atom of thealkyl group is replaced with the aryl group. The aralkyl grouppreferably has, for example, 7 to 15 carbon atoms. Specific examplesthereof include a benzyl group, a 1-phenylethyl group, a 2-phenylethylgroup, a 1-phenylpropyl group, and a 3-naphthylpropyl group.

An example of the cycloalkyl group as the substituent in the aliphaticcarboxylic acids is a monocyclic, polycyclic, or condensed cycloalkylgroup with 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, andmore preferably 3 to 10 carbon atoms. Specific examples thereof includea cyclopropyl group, a cyclopentyl group, and a cyclohexyl group.

An example of the alkoxy group as the substituent in the aliphaticcarboxylic acids is an alkoxy group in which a linear, branched, orcyclic alkyl group or cycloalkyl group with 1 to 20 carbon atoms(preferably 1 to 15 carbon atoms, and more preferably 1 to 10 carbonatoms (if cyclic, at least 3 carbon atoms)) is bonded to an oxygen atom.Specific examples thereof include a methoxy group, an ethoxy group, ann-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxygroup, an s-butoxy group, a t-butoxy group, an n-pentyloxy group, ann-hexyloxy group, an n-octyloxy group, a cyclopentyloxy group, and acyclohexyloxy group.

An example of the aryloxy group as the substituent in the aliphaticcarboxylic acids is an aryloxy group in which a monocyclic, polycyclic,or condensed aryl group with 6 to 36 carbon atoms (preferably 6 to 18carbon atoms, and more preferably 6 to 14 carbon atoms) is bonded to anoxygen atom. Specific examples thereof include a phenoxy group, atolyloxy group, a xylyloxy group, and a naphthoxy group.

An example of the aralkyloxy group as the substituent in the aliphaticcarboxylic acids is a group in which at least one hydrogen atom of thealkyl group or the cycloalkyl group in the alkoxy group is replaced withthe aryl group. The aralkyloxy group preferably has, for example, 7 to15 carbon atoms. Specific examples thereof include a benzyloxy group, a1-phenylethoxy group, a 2-phenylethoxy group, a 1-phenylpropoxy group, a2-phenylpropoxy group, a 3-phenylpropoxy group, a 4-phenylbutoxy group,a 1-naphthylmethoxy group, and a 2-naphthylmethoxy group.

Examples of the halogen atom as the substituent in the aliphaticcarboxylic acids include fluorine, chlorine, bromine, and iodine.

Examples of the heterocyclic group as the substituent in the aliphaticcarboxylic acids include an aliphatic heterocyclic group and an aromaticheterocyclic group. An example of the aliphatic heterocyclic group is,for example, a 3- to 8-membered (preferably, 4- to 6-membered)monocyclic, polycyclic, or condensed aliphatic heterocyclic group with 2to 14 carbon atoms and at least one heteroatom (preferably, 1 to 3heteroatoms) such as a nitrogen atom, an oxygen atom and/or a sulfuratom. Specific examples of the aliphatic heterocyclic group include anazetidyl group, an azetidino group, a pyrrolidyl group, a pyrrolidinogroup, a piperidinyl group, a piperidino group, a piperazinyl group, apiperazino group, a morpholinyl group, a morpholino group, atetrahydrofuryl group, a tetrahydropyranyl group, and atetrahydrothiophenyl group. Meanwhile, an example of the aromaticheterocyclic group is, for example, a 3- to 8-membered (preferably, 5-or 6-membered) monocyclic, polycyclic, or condensed heteroaryl groupwith 2 to 15 carbon atoms and at least one heteroatom (preferably, 1 to3 heteroatoms) such as a nitrogen atom, an oxygen atom and/or a sulfuratom. The specific examples thereof include a furyl group, a thienylgroup, a pyridyl group, a pyrimidyl group, a pyrazyl group, a pyridazylgroup, a pyrazolyl group, an imidazolyl group, an oxazolyl group, athiazolyl group, a benzofuryl group, a benzothienyl group, a quinolylgroup, an isoquinolyl group, a quinoxalyl group, a phthalazyl group, aquinazolyl group, a naphthyridyl group, a cinnolyl group, abenzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, anacridyl group, and an acridinyl group.

Examples of the optionally-protected amino group as the substituent inthe aliphatic carboxylic acids include: unprotected amino groups; mono-and di-alkylamino groups such as a N-methylamino group, aN,N-dimethylamino group, a N,N-diethylamino group, aN,N-diisopropylamino group, and a N-cyclohexylamino group; mono- anddi-arylamino groups such as a N-phenylamino group, a N,N-diphenylaminogroup, a N-naphthylamino group, and a N-naphthyl-N-phenylamino group;mono- and di-aralkylamino groups such as a N-benzylamino group and aN,N-dibenzylamino group; acylamino groups such as a formylamino group,an acetylamino group, a propionylamino group, a pivaloylamino group, apentanoylamino group, a hexanoylamino group, and a benzoylamino group;alkoxycarbonylamino groups such as a methoxycarbonylamino group, anethoxycarbonylamino group, an n-propoxycarbonylamino group, ann-butoxycarbonylamino group, a tert-butoxycarbonylamino group, apentyloxycarbonylamino group, and a hexyloxycarbonylamino group;aryloxycarbonylamino groups such as a phenyloxycarbonylamino group; andaralkyloxycarbonylamino groups such as a benzyloxycarbonylamino group.Other examples of the optionally-protected amino group include thoseprotected by common protective groups for the amino group described in,for example, Reference Document 1 (Protective Groups in OrganicSynthesis; Second Edition, JOHN WIREY & SONS, INC. 1991).

Furthermore, examples of the optionally-protected hydroxy group as thesubstituent in the aliphatic carboxylic acids include unprotectedhydroxy groups and hydroxy groups that may be protected by commonprotective groups for hydroxy groups which are described in, forexample, Reference Document 1, and which includes, for example, amethoxymethyl group, a benzyl group, and silyl groups such astrialkylsilyl groups (a trimethylsilyl group, a t-butyldimethylsilylgroup, and the like). Note that, when the protective group is an acylgroup, a resultant product may have the protective group reduced.

The alkyl group, the aryl group, the aralkyl group, the cycloalkylgroup, the alkoxy group, the aralkyloxy group, the aryloxy group, andthe heterocyclic group, which are listed as the substituent in thealiphatic carboxylic acids, may also have a substituent such as an alkylgroup, an aryl group, an aralkyl group, a cycloalkyl group, an alkoxygroup, an aralkyloxy group, an aryloxy group, a halogen atom, aheterocyclic group, an optionally-protected amino group, and anoptionally-protected hydroxy group, which have been described above.

Examples of the aromatic carboxylic acids include: monocyclic,polycyclic, or condensed aryl groups with 6 to 36 carbon atoms,preferably 6 to 18 carbon atoms, and more preferably 6 to 12 carbonatoms; and mono- and polyaromatic carboxylic acids having a 3- to8-membered (preferably, 5- to 8-membered) monocyclic, polycyclic, orcondensed heteroaryl group with 1 to 4 heteroatoms (preferably 1 to 3heteroatoms, more preferably 1 to 2 heteroatoms) such as a nitrogenatom, an oxygen atom, and a sulfur atom. Specific examples thereofinclude benzoic acid, naphthalenecarboxylic acid, pyridinecarboxylicacid, pyridinedicarboxylic acid, quinolinecarboxylic acid,furancarboxylic acid, and thiophenecarboxylic acid.

These aromatic carboxylic acids may also have a substituent such as analkyl group, an aryl group, an aralkyl group, a cycloalkyl group, analkoxy group, an aryloxy group, an aralkyloxy group, a halogen atom, aheterocyclic group, an optionally-protected amino group, and anoptionally-protected hydroxy group, which have been described as thesubstituent in the aliphatic carboxylic acids.

On the other hand, examples of the lactones used in the presentinvention include β-lactone, γ-lactone, and δ-lactone. These lactonesmay have a substituent such as an alkyl group, an aryl group, an aralkylgroup, a cycloalkyl group, an alkoxy group, an aryloxy group, anaralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, and an optionally-protected hydroxygroup, which have been described as the substituent in the aliphaticcarboxylic acids. Moreover, the lactones may have a bicyclo-ringstructure or a condensed structure with an aromatic ring.

Meanwhile, examples of alkyl groups in the alkyl esters, aryl groups inthe aryl esters, aralkyl groups in the aralkyl esters, and cycloalkylgroups in the cycloalkyl esters respectively include those that havebeen described as the substituents in the aliphatic carboxylic acids.Furthermore, these groups may have a substituent such as an alkyl group,an aryl group, an aralkyl group, a cycloalkyl group, an alkoxy group, anaralkyloxy group, an aryloxy group, a halogen atom, a heterocyclicgroup, an optionally-protected amino group, and an optionally-protectedhydroxy group, which have been described as the substituent in thealiphatic carboxylic acids.

Preferable examples of the esters include alkyl esters with 1 to 10carbon atoms, and preferably 1 to 5 carbon atoms, such as methyl ester,ethyl ester, and isopropyl ester. Amore preferable example of the estersis methyl ester.

Each of these esters does not necessarily have to have an asymmetriccenter. The ester may be an optically active substance or a mixture ofvarious isomers.

The alcohol production method of the present invention is suitablyperformed without a solvent or in a solvent. However, it is preferableto use a solvent. The solvent is preferably capable of dissolving thesubstrate and the catalyst. A single solvent or a mixed solvent is used.Specific examples thereof include: aromatic hydrocarbons such as tolueneand xylene; aliphatic hydrocarbons such as hexane and heptane;halogenated hydrocarbons such as dichloromethane and chlorobenzene;ethers such as diethyl ether, tetrahydrofuran, methyl t-butyl ether, andcyclopentyl methyl ether; alcohols such as methanol, ethanol,isopropanol, n-butanol, and 2-butanol; and polyvalent alcohols such asethylene glycol, propylene glycol, 1,2-propanediol and glycerin. Amongthem, ethers are preferable, and tetrahydrofuran is particularlypreferable, as the solvent. The amount of the solvent can beappropriately selected, depending on reaction conditions and the like.The reaction is conducted with stirring as necessary.

The amount of the catalyst differs, depending on the hydrogenationsubstrate, the reaction conditions, the type of the catalyst, and thelike. However, the molar ratio of a ruthenium metal to the hydrogenationsubstrate is normally in the range of 0.001 mol % to 10 mol %, andpreferably 0.05 mol % to 5 mol %.

In the method of the present invention, the reaction temperature at thetime of hydrogen reduction is 50° C. to 150° C., and preferably 60° C.to 120° C. If the reaction temperature is too low, a large amount of thematerial may remain unreacted. Meanwhile, if the reaction temperature istoo high, the material, the catalyst, and the like may decompose. Thus,such extreme conditions are not favorable.

In the present invention, the hydrogen pressure at the time of hydrogenreduction is 1 MPa to 10 MPa, and preferably 3 MPa to 6 MPa.

The reaction time of approximately 2 hours to 20 hours allows obtaininga sufficiently high material conversion rate.

After the reaction is completed, normally-used purification techniquessuch as extraction, filtration, crystallization, distillation, andvarious chromatography techniques are performed singly or in combinationas appropriate. In this manner, a targeted alcohol can be obtained.

In the present invention, specific examples of an organic base compoundin a base compound include amines such as triethylamine,diisopropylethylamine, N,N-dimethylaniline, piperidine, pyridine,4-dimethylaminopyridine, 1,5-diazabicyclo[4.3.0]nona-5-ene,1,8-diazabicyclo[5.4.0]undeca-7-ene, tri-n-butylamine, andN-methylmorpholine.

Meanwhile, specific examples of an inorganic base compound in the basecompound include: alkali metal carbonates such as potassium carbonate,sodium carbonate, lithium carbonate, and cesium carbonate; alkalineearth metal carbonates such as magnesium carbonate and calciumcarbonate; alkali metal bicarbonates such as sodium bicarbonate andpotassium bicarbonate; alkali metal hydroxides such as sodium hydroxide,potassium hydroxide, and lithium hydroxide; alkaline earth metalhydroxides such as magnesium hydroxide and calcium hydroxide; alkalimetal alkoxides such as sodium methoxide, sodium ethoxide, sodiumisopropoxide, sodium t-butoxide, potassium methoxide, potassiumethoxide, potassium isopropoxide, potassium t-butoxide, lithiummethoxide, lithium isopropoxide, and lithium t-butoxide; alkaline earthmetal alkoxides such as magnesium methoxide and magnesium ethoxide; andmetal hydrides such as sodium hydride and calcium hydride.

A ruthenium compound is used as a starting material for producing aruthenium complex used in the present invention. Examples of theruthenium compound include: inorganic ruthenium compounds such as RuCl₃hydrate, RuBr₃ hydrate, and RuI₃ hydrate; and RuCl₂(DMSO)₄,[Ru(cod)Cl₂]_(n), [Ru(nbd)Cl₂]_(n), (COD)Ru(2-methallyl)₂.[Ru(benzene)Cl₂]₂. [Ru(benzene)Br₂]₂. [Ru(benzene)I₂]₂,[Ru(p-cymene)Cl₂]₂, [Ru(p-cymene)Br₂]₂, [Ru(p-cymene)I₂]₂,[Ru(mesitylene)Cl₂]₂, [Ru(mesitylene)Br₂]₂, [Ru(mesitylene)I₂]₂,[Ru(hexamethylbenzene) Cl₂]₂, [Ru(hexamethylbenzene)Br₂]₂,[Ru(hexamethylbenzene)I₂]₂, RuCl₂ (PPh₃)₃, RuBr₂(PPh₃)₃, RuI₂(PPh₃)₃,RuH₄ (PPh₃)₃, RuClH(PPh₃)₃, RuH(OAc)(PPh₃)₃, and RuH₂(PPh₃)₄. In theabove examples, DMSO represents dimethylsulfoxide, cod represents1,5-cyclooctadiene, nbd represents norbornadiene, and Ph represents aphenyl group.

Next, a ruthenium complex used as the catalyst in the present inventionwill be described. The ruthenium complex is represented by the followinggeneral formula (1):RuH(X)(L¹)(L²)_(n)  (1)wherein X represents a monovalent anionic ligand; L¹ represents atetradentate ligand having at least one coordinating phosphino group andat least one coordinating amino group or a bidentate aminophosphineligand having one coordinating phosphino group and one coordinatingamino group; L² represents a bidentate aminophosphine ligand having onecoordinating phosphino group and one coordinating amino group, providedthat n is 0 when L¹ is the tetradentate ligand, and n is 1 when L¹ isthe bidentate ligand.

First, the monovalent anionic ligand represented by X in the generalformula (1) will be described. Examples of the monovalent anionic ligandinclude a hydrogen atom (hydride), AlH₄, BH₄, ligands represented by thefollowing general formulae (8), (9a) and (9b), a halogen atom, an alkoxygroup, an aryloxy group, an aralkyloxy group, a hydroxy group, anacyloxy group, and a sulfonyloxy group.

wherein M represents aluminium or boron; r is a natural number between 0to 3 inclusive; R²⁵ represents an alkyl group which may have asubstituent, an aryl group which may have a substituent, an aralkylgroup which may have a substituent, a cycloalkyl group which may have asubstituent, an alkoxy group which may have a substituent, an aryloxygroup which may have a substituent, or an aralkyloxy group which mayhave a substituent; R²⁶ and R²⁶′, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, an aralkyl group which mayhave a substituent, or a cycloalkyl group which may have a substituent;R²⁶ and another R²⁶, or R²⁶ and R^(26′) may bond to each other to form aring; and Q^(9a) and Q^(9b) each independently represent a divalentarylene group which may have a substituent or an alkylene group whichmay have a substituent.

Here, the alkyl group, the aryl group, the aralkyl group, the cycloalkylgroup, the alkoxy group, the aryloxy group, and the aralkyloxy group arethe same as those that have been described as the substituent in thealiphatic carboxylic acids. Examples of the substituents which thesegroups may have include an alkyl group, an aryl group, an aralkyl group,a cycloalkyl group, an alkoxy group, an aralkyloxy group, an aryloxygroup, a halogen atom, a heterocyclic group, an optionally-protectedamino group, an optionally-protected hydroxy group, and the like, whichhave been described as the substituent in the aliphatic carboxylicacids.

An example of the divalent arylene groups represented by Q^(9a) andQ^(9b) is a divalent group which is composed of a monocyclic orcondensed aryl group with 6 to 12 carbon atoms. Examples of the divalentgroup include a phenylene group and a 2,3-naphthalenediyl group.Examples of the phenylene group include an o-phenylene group and anm-phenylene group. An example of the alkylene group is a linear orbranched alkyl group with 1 to 20 carbon atoms, preferably 1 to 10carbon atoms, and more preferably 1 to 6 carbon atoms. Specific examplesthereof include a methylene group, an ethylene group, a trimethylenegroup, a tetramethylene group, and a pentamethylene group. Furthermore,the alkylene group may be a cycloalkylene group. An example of thecycloalkylene group is a divalent group composed of a monocyclic,polycyclic, or condensed cycloalkyl group with 3 to 15 carbon atoms,preferably 3 to 10 carbon atoms, and more preferably 3 to 6 carbonatoms. Specific examples thereof include a cyclopropylene group, acyclobutylene group, a cyclopentylene group, and a cyclohexylene group.Examples of the substituents which these groups may have include analkyl group, an aryl group, an aralkyl group, a cycloalkyl group, analkoxy group, an aryloxy group, an aralkyloxy group, a halogen atom, aheterocyclic group, an optionally-protected amino group, anoptionally-protected hydroxy group, and the like, which have beendescribed as the substituent in the aliphatic carboxylic acids.

The alkyl group, the aryl group, the aralkyl group, the cycloalkylgroup, the alkoxy group, the aryloxy group, the aralkyloxy group, andthe heterocyclic group may have a substituent that has been described,such as an alkyl group, an aryl group, an aralkyl group, a cycloalkylgroup, an alkoxy group, an aryloxy group, an aralkyloxy group, a halogenatom, a heterocyclic group, an optionally-protected amino group, and anoptionally-protected hydroxy group. Examples of Q^(9a) and Q^(9b)include a 2,2,2-trifluoroethoxy group, a1,1,1,3,3,3-hexafluoro-2-propoxy group, a 1-pentafluorophenylethoxygroup, and a pentafluorophenoxy group. The monovalent anionic ligand ofthe general formulae (9a) and (9b) may be represented by the followingstructural formulae 9A and 9B.

The acyloxy group may be represented by (R^(a)CO₂). Examples of R^(a) inthe acyloxy group R^(a)CO₂ include a hydrogen atom, an alkyl group, anaryl group, an aralkyl group, and a cycloalkyl group. The alkyl group,the aryl group, the aralkyl group, and the cycloalkyl group are the sameas those that have been described as the substituent in the aliphaticcarboxylic acids. These groups may further have a substituent such as analkyl group, an aryl group, an aralkyl group, a cycloalkyl group, analkoxy group, an aralkyloxy group, an aryloxy group, a halogen atom, aheterocyclic group, an optionally-protected amino group, and anoptionally-protected hydroxy group, which have been described as thesubstituent in the aliphatic carboxylic acids. Specific examples ofR^(a) include a methyl group, an ethyl group, a propyl group, a t-butylgroup, a trifluoromethyl group, a phenyl group, and a pentafluorophenylgroup.

The sulfonyloxy group may be represented by (R^(S)SO₃). Examples of theR^(S) in the sulfonyloxy group R^(S)SO₃ are the same as those of R^(a)in the acyloxy group.

The ruthenium complex represented by the general formula (1) can beobtained by methods described in, for example, Chem. Eur. J. 2003, 9,4954, Adv. Synth. Catal. 2005, 347, 571, and the like. The complex thusprepared may have its stereoisomer due to the coordination andconformation of the ligands. The complex used in the present reactionmay be a mixture of such stereoisomers or a single pure isomer.

In addition, according to the methods described in, for example, J. Am.Chem. Soc. 2005, 127, 516 and Organomet. 2007, 26, 5940 described above,a ruthenium hydride complex represented by the general formula (1)wherein X═BH₄ can be obtained. Such complexes exist relatively stably,and are relatively easy to handle.

Next, the tetradentate ligand which is represented by L¹ in the generalformula (1), and which is used in the present invention, will bedescribed. The tetradentate ligand is preferably a ligand having atleast one coordinating phosphino group and at least one coordinatingamino group, and more preferably a ligand further having onecoordinating phosphorus atom and one coordinating nitrogen atom, andmost preferably an aminophosphine ligand having two coordinatingphosphino groups and two coordinating amino groups.

Specifically, the tetradentate ligand may be represented by, forexample, the following general formula (2):

wherein R¹, R², R³, R⁴, R⁵ and R⁶, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aralkyl group which may have a substituent, an aryl group which mayhave a substituent, or a cycloalkyl group which may have a substituent;R¹ and another R¹, R¹ and either R², R³ or R⁴, R³ and R⁴, or R⁵ and R⁶may bond to each other to form a ring; and Q² and Q², which may be sameor different, each represent a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond.

The alkyl group, the aryl group, the aralkyl group, and the cycloalkylgroup represented by R¹, R², R³, R⁴, R⁵ and R⁶ in the formula are thesame as those that have been described as the substituent in thealiphatic carboxylic acids. Examples of the substituents which thesegroups may have include an alkyl group, an aryl group, an aralkyl group,a cycloalkyl group, an alkoxy group, an aryloxy group, an aralkyloxygroup, a halogen atom, a heterocyclic group, an optionally-protectedamino group, an optionally-protected hydroxy group, and the like, whichhave been described as the substituent in the aliphatic carboxylicacids.

An example of the divalent arylene groups represented by Q² and Q² is adivalent group which is composed of a monocyclic or condensed aryl groupwith 6 to 12 carbon atoms. Examples thereof include a phenylene groupand a 2,3-naphthalenediyl group. Examples of the phenylene group includean o-phenylene group and an m-phenylene group. An example of thealkylene group is a linear or branched alkyl group with 1 to 20 carbonatoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 6carbon atoms. Specific examples thereof include a methylene group, anethylene group, a trimethylene group, a tetramethylene group, and apentamethylene group. Furthermore, the alkylene group may be acycloalkylene group. An example of the cycloalkylene group is a divalentgroup composed of a monocyclic, polycyclic, or condensed cycloalkylgroup with 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, andmore preferably 3 to 6 carbon atoms. Specific examples of the divalentgroup include a cyclopropylene group, a cyclobutylene group, acyclopentylene group, and a cyclohexylene group. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids.

The ligand represented by the general formula (2) does not necessarilyhave to be an optically active substance. The ligand may be an opticallyactive substance, a racemic body, or a mixture of various stereoisomers,depending on Q¹, Q², R¹, R², R³, R⁴, R⁵ and R⁶.

Next, the bidentate ligands used in the present invention will bedescribed.

The bidentate ligands represented by L¹ and L² in the general formula(1) are each preferably an aminophosphine ligand having a coordinatingphosphorus atom and a coordinating nitrogen atom.

Specifically, the bidentate ligand may be represented by, for example,the following general formula (3).

wherein R⁷, R⁸, R⁹, R²⁰ and R¹¹, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, an aralkyl group which mayhave a substituent, or an cycloalkyl group which may have a substituent;R⁷ and R⁸ or R⁹, R⁸ and R⁹, or R¹⁰ and R¹¹ may bond to each other toform a ring; and Q³ represents a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond.

In the general formula (3), R⁷, R⁸, R⁹, R¹⁰ and R¹¹ are the same as R¹,R², R³, R⁴, R⁵ and R⁶ in the general formula (2) described above.Likewise, Q³ in the general formula (3) is the same as Q¹ and Q² in thegeneral formula (2) described above.

The ligand represented by the general formula (3) does not necessarilyhave to be an optically active substance. The ligand may be an opticallyactive substance, a racemic body, or a mixture of various stereoisomers,depending on Q³, R⁷, R⁸, R⁹, R²⁰ and R¹¹.

Next, a tetradentate ligand which has an imine structure, and which isused in the present invention, will be described. The tetradentateligand is represented by a general formula (4) or (5):

wherein R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹, which maybe same or different, each represent a hydrogen atom, an alkyl groupwhich may have a substituent, an aryl group which may have asubstituent, an aralkyl group which may have a substituent, or acycloalkyl group which may have a substituent; R¹² and another R¹², R¹²and R¹³ or R¹⁴, R¹³ and R¹⁴, R¹⁵ and R¹⁶, R¹⁷ and another R¹⁷, R¹⁹ andR¹⁷ or R¹⁸, or R²⁰ and R²¹ may bond to each other to form a ring; andQ⁴, Q⁵, Q⁶ and Q⁷, which may be same or different, each represent adivalent arylene group which may have a substituent, an alkylene groupwhich may have a substituent, or a bond.

In the general formulae (4) and (5), R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸,R¹⁹, R²⁰ and R²¹ are the same as R¹, R², R³, R⁴, R⁵, and R⁶ in thegeneral formula (2). Likewise, Q⁴, Q⁵, Q⁶ and Q⁷ in the general formulae(4) and (5) are the same as Q¹ and Q² in the general formula (2).

Next, a bidentate ligand which has an imine structure, and which is usedin the present invention, will be described. The bidentate ligand isrepresented by general formulae (7a) and (7b).

wherein R²², R²³, R²⁴, R²⁵, R¹⁰⁰, R¹⁰¹, R¹⁰², R¹⁰³, R¹⁰⁴ and R¹⁰⁵, whichmay be same or different, each represent a hydrogen atom, an alkyl groupwhich may have a substituent, an aryl group which may have asubstituent, an aralkyl group which may have a substituent, or acycloalkyl group which may have a substituent; R²² and R²³, R²⁴ and R²⁵,or R¹⁰⁴ and R¹⁰⁵ may bond to each other to form a ring; and Q^(7a) andQ^(7b) each represent a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond.

In the general formulae (7a) and (7b), R²², R²³, R²⁴, R²⁵, R¹⁰⁰, R¹⁰¹,R¹⁰², R¹⁰³, R¹⁰⁴ and R¹⁰⁵ are the same as R¹, R², R³, R⁴, R⁵ and R⁶ inthe general formula (2). Likewise, Q^(7a) and Q^(7b) in the generalformulae (7a) and (7b) are the same as Q¹ and Q² in the general formula(2).

Next, the ruthenium complexes used as the catalyst in the presentinvention will be described. The ruthenium complexes are represented bygeneral formulae (6) and (6′):[Ru(X¹)_(k)(X²)_(l)(Y¹)_(m)(Y²)_(o)(L^(1′))](Z)_(q)  (6)[Ru(X³)_(k′)(X⁴)_(l′)(Y³)_(m′)(Y⁴)_(o′)(L^(1″))(L^(2″))](Z′)_(q′)  (6′)wherein X¹, X², X³ and X⁴ each independently represent a monovalentanionic ligand; Y¹, Y², Y³ and Y⁴ each independently represent a neutralmonodentate ligand; Z and Z′ each represent a monovalent anion that doesnot coordinate to a metal; L^(1′) represents the tetradentate ligandrepresented by the general formula (4) or (5); L^(1″) and L^(2″), whichmay be same or different, each represent the bidentate ligandrepresented by the general formula (7a) or (7b), provided that: k, l, mand o are each a natural number between 0 to 2 inclusive, and satisfy0≦k+l+m+o≦2; q is 0 when k+1=2, q is 1 when k+1=1, and q is 2 whenk+1=0; k′, l′, m′ and o′ are each a natural number between 0 to 2inclusive, and satisfy 0≦k′+l′+m′+o′≦2; and q′ is 0 when k′+l′=2, q′ is1 when k′+l′=1, and q′ is 2 when k′+l′=0.

In the general formulae (6) and (6′), X¹, X², X³ and X⁴ are the same asX in the general formula (1). Examples of Y¹, Y², Y³ and Y⁴ in thegeneral formulae (6) and (6′) include water, alcohols, ethers, amines,amides, nitriles, sulfides, sulfoxides, phosphines, and phosphineoxides.

The alcohols may be represented by, for example, the following generalformula (10):R²⁷—OH  (10)wherein R²⁷ represents an alkyl group which may have a substituent, anaralkyl group which may have a substituent, an aryl group which may havea substituent, or a cycloalkyl group which may have a substituent.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids.

Preferable examples of the alcohols are lower alcohols with 1 to 4carbon atoms. More specific examples thereof include methanol, ethanol,n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol,2,2,2-trifluoroethanol, and 1, 1, 1, 3,3,3-hexafluoro-2-propanol.

The ethers may be represented by, for example, the following generalformula (11):R²⁸—O—R²⁹  (11)wherein R²⁸ and R²⁹, which may be same or different, each represent analkyl group which may have a substituent, an aralkyl group which mayhave a substituent, an aryl group which may have a substituent, or acycloalkyl group which may have a substituent; alternatively, R²⁸ andR²⁹ may bond to each other to form a cyclic ether.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the ethers includecyclic and acyclic ethers with 2 to 12 carbon atoms. More specificexamples thereof include diethyl ether, diisopropyl ether, tert-butylmethyl ether, cyclopentyl methyl ether, tetrahydrofuran, and1,4-dioxane.

The amines may be represented by, for example, the following generalformula (12):R³⁰R³¹R³²N  (12)wherein R³⁰, R³¹ and R³², which may be same or different, each representa hydrogen atom, an alkyl group which may have a substituent, an aralkylgroup which may have a substituent, an aryl group which may have asubstituent, or a cycloalkyl group which may have a substituent;alternatively, R³⁰ and R³¹ and/or R³² may bond to each other to form aring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the amines includealiphatic and aromatic amines such as triethylamine, tri-n-butylamine,triphenylamine, pyridine, dimethylaminopyridine, and pyrimidine.

The amides may be represented by, for example, the following generalformula (13):

wherein R³³, R³⁴ and R³⁵, which may be same or different, each representa hydrogen atom, an alkyl group which may have a substituent, an aralkylgroup which may have a substituent, an aryl group which may have asubstituent, or a cycloalkyl group which may have a substituent;alternatively, R³³ and R³⁴ and/or R³⁵ may bond to each other to form aring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the amides includedimethylformamide, dimethylacetamide, and benzamide.

The nitriles may be represented by, for example, the following generalformula (14):R³⁶—CN  (14)wherein R³⁶ represents an alkyl group which may have a substituent, anaralkyl group which may have a substituent, an aryl group which may havea substituent, or a cycloalkyl group which may have a substituent.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the nitriles includeacetonitrile and benzonitrile.

The sulfides may be represented by, for example, the following generalformula (15):R³⁷—S—R³⁸  (15)wherein R³⁷ and R³⁸, which may be same or different, each represent analkyl group which may have a substituent, an aralkyl group which mayhave a substituent, an aryl group which may have a substituent, or acycloalkyl group which may have a substituent; alternatively, R³⁷ andR³⁸ may bond to each other to form a ring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the sulfides includedimethylsulfide, tetrahydrothiophene, thioanisole, and thiophene.

The sulfoxides may be represented by, for example, the following generalformula (16):

wherein R³⁹ and R⁴⁰, which may be same or different, each represent analkyl group which may have a substituent, an aralkyl group which mayhave a substituent, an aryl group which may have a substituent, or acycloalkyl group which may have a substituent; alternatively, R³⁹ andR⁴⁹ may bond to each other to form a ring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the sulfoxidesinclude dimethylsulfoxide and tetramethylenesulfoxide.

The phosphines may be represented by, for example, the following generalformula (17):R⁴¹R⁴²R⁴³p  (17)wherein R⁴¹, R⁴² and R⁴³, which may be same or different, each representa hydrogen atom, an alkyl group which may have a substituent, an aralkylgroup which may have a substituent, an aryl group which may have asubstituent, or a cycloalkyl group which may have a substituent;alternatively, R⁴¹ and R⁴² and/or R⁴³ may bond to each other to form aring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the phosphinesinclude triphenylphosphine, tritolylphosphine, trimethylphosphine,triethylphosphine, methyldiphenylphosphine, and dimethylphenylphosphine.

The phosphine oxides may be represented by, for example, the followinggeneral formula (18):

wherein R⁴⁴, R⁴⁵ and R⁴⁶, which may be same or different, each representa hydrogen atom, an alkyl group which may have a substituent, an aralkylgroup which may have a substituent, an aryl group which may have asubstituent, or a cycloalkyl group which may have a substituent;alternatively, R⁴⁴ and R⁴⁵ and/or R⁴⁶ may bond to each other to form aring.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, an aryloxygroup, an aralkyloxy group, a halogen atom, a heterocyclic group, anoptionally-protected amino group, an optionally-protected hydroxy group,and the like, which have been described as the substituent in thealiphatic carboxylic acids. Preferable examples of the phosphine oxidesinclude oxides of the aforementioned phosphines.

Additionally, examples of Z and Z′ in the general formulae (6) and (6′)include anions of BF₄, B(C₆F₅)₄, BPh₄, PF₆, ClO₄, OTf, and the like.Here, Tf represents a trifluoromethanesulfonyl group.

Furthermore, a method of conducting the reaction with a complex obtainedby reducing the ruthenium complex of the general formula (6) or (6′)will be described. Examples of the reducing agent used in the methodinclude: aluminium hydride compounds such as lithium aluminium hydride(LAH), lithium alkoxyaluminium hydrides represented by the followinggeneral formula (19), sodium bis (2-methoxyethoxy) aluminium hydride(Red-Al) diisobutylaluminium hydride (DIBAH); boron hydride compoundssuch as sodium borohydride, potassium borohydride, lithium borohydride,tetraalkylammonium borohydrides represented by the following generalformula (20), zinc borohydride, sodium cyanoboronhydride,tetraalkylammonium cyanoborohydrides represented by the followinggeneral formula (21), lithium triethylborohydride (Super-Hydride)lithium tri(-sec-butyl)borohydride (L-Selectride), potassiumtri(-sec-butyl)borohydride (K-Selectride), lithium9-borabicyclo[3.3.1]nonane hydride (Li 9-BBN hydride), a borane-dimethylsulfide complex, a borane-tetrahydrofuran complex,9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane; and molecularhydrogen:Li(R⁴⁷O)_(j)AlH_((4-j))  (19)(R⁴⁸)₄NBH₄  (20), and(R⁴⁹)₄NCNBH₃  (21)wherein R⁴⁷ represents an alkyl group which may have a substituent, anaralkyl group which may have a substituent, an aryl group which may havea substituent, or a cycloalkyl group which may have a substituent; R⁴⁸and R⁴⁹ each represent an alkyl group which may have a substituent; andj represents a natural number between 1 to 3 inclusive.

Here, the alkyl group, the aryl group, the aralkyl group, and thecycloalkyl group are the same as those that have been described as thesubstituent in the aliphatic carboxylic acids. Examples of thesubstituents which these groups may have include an alkyl group, an arylgroup, an aralkyl group, a cycloalkyl group, an alkoxy group, anaralkyloxy group, an aryloxy group, a halogen atom, a heterocyclicgroup, an optionally-protected amino group, an optionally-protectedhydroxy group, and the like, which have been described as thesubstituent in the aliphatic carboxylic acids.

The ruthenium complex of the general formula (6) or (6′) is reduced in asolvent. The solvent is a single solvent or a mixed solvent. Specificexamples thereof include: aromatic hydrocarbons such as toluene andxylene; aliphatic hydrocarbons such as hexane and heptane; halogenatedhydrocarbons such as dichloromethane and chlorobenzene; ethers such asdiethyl ether, tetrahydrofuran, methyl t-butyl ether, and cyclopentylmethyl ether; alcohols such as methanol, ethanol, isopropanol,n-butanol, and 2-butanol; and polyvalent alcohols such as ethyleneglycol, propylene glycol, 1,2-propanediol and glycerin. Among them, thesolvent desirably contains primary or secondary alcohols. Particularlypreferable solvents are methanol, ethanol, and a mixed solvent oftoluene and these. The amount of the solvent can be appropriatelyselected, depending on reaction conditions and the like. The reaction isconducted with stirring as necessary.

Conventionally, the ruthenium hydride complex which is represented bythe general formula (1) and which includes an aminophosphine ligand asrepresented by the general formula (2) or (3) has not been able to beobtained in a single step from a ruthenium complex including animinophosphine ligand. In contrast, use of the method described in thepresent invention makes it possible to efficiently prepare the rutheniumhydride complex in fewer steps, and accordingly to simplify theproduction process.

Additionally, the complex obtained through the reduction step may beused as the catalyst without being isolated from the reaction solution.

By using such a ruthenium complex as the catalyst, alcohols can beproduced from an ester and a lactone at high yield and at high catalyticefficiency under relatively low hydrogen pressure and reactiontemperature which are industrially advantageous. Additionally, theruthenium complex used in the present reaction catalyzes the reactionwithout adding a base. Thus, even when the ester or the lactone to bereduced is labile to a base, the ester and the lactone can be reduced toalcohols without undesirable side-reactions such as decomposition andpolymerization. Moreover, even when the ester or the lactone is anoptically active substance, the ester and the lactone can be reduced toalcohols without lowering the optical purity.

EXAMPLES

The present invention will be described in detail below with referenceto the following non-limiting Examples and Comparative example.

Note that, ¹H-NMR and ³¹P-NMR spectra were measured using MERCURY plus300 manufactured by Varian, Inc. Additionally, the conversion rate, theselectivity and the optical purity were measured by gas chromatography(GC) and liquid chromatography (LC). The instruments used in theExamples are as follows.

-   A. Conversion rate and selectivity-   A-1. Conversion rate-selectivity analysis condition A: used for    analyses in Examples 1 to 5, 8, 11 to 15, 19, 20 and 23 and    Comparative Examples 1 to 4    -   Capillary; HP-INNOWax-   Injection temperature: 250° C., detection temperature: 250° C.    80° C. (1 min.) −10° C./min. −250° C. (12 min.)-   A-2. Conversion rate-selectivity analysis condition B: used for    analyses in Examples 9 and 10 and Comparative Example 10    -   GC; capillary RTx-5-   Injection temperature: 250° C., detection temperature: 250° C.    80° C. (10 min.)−10° C./min.−270° C. (1 min.)-   A-3. Conversion rate-selectivity analysis condition C: used for    analyses in Examples 16 and 21    -   GC; capillary TC-FFAP-   Injection temperature: 250° C., detection temperature: 250° C. 80°    C.−5° C./min.−220° C. (2 min.)-   B. Optical purity-   B-1. Optical purity: optical purity analysis of 2-Boc-aminopropanol

The analysis was performed after the conversion into p-nitrobenzoateester.

-   HPLC; Column DAICEL CHIRALCEL OD-H-   Oven; 40° C., eluent; hexane:2-propanol=95:5-   B-2. Optical purity: Example 8 and Comparative Example 9 HPLC;    Column DAICEL CHIRALCEL OJ-H-   Oven; 30° C., eluent; hexane:2-propanol=98:2-   B-3. Optical purity: Optical purity analysis of 3-amino-1-butanol

The analysis was performed after the trifluoroacetylation of the aminogroup and the hydroxy group.

-   GC; capillary β-DEX225-   Injection temperature: 250° C., detection temperature: 250° C.    160° C. (15 min.)-   B-4. Optical purity: optical purity analysis of 1,2-propanediol

The analysis was performed after the trifluoroacetylation of the hydroxygroup.

-   GC; capillary CHIRASIL-DEX-CB-   Injection temperature: 250° C., detection temperature: 250° C.    45° C. (15 min.)−10° C./min.−125° C.-   B-5. Optical purity: optical purity analysis of 1,3-butanediol GC;    capillary BETA-DEX™225-   Injection temperature: 250° C., detection temperature: 250° C.    120° C. (30 min.)

Example 1 Synthesis of Ruthenium Complex 1 and Ester Reduction Using theSame

[RuClH(PPh₃)₃] (1.73 mmol) and L^(1a) (1.73 mmol) were charged into a100 mL-flask, and air inside the flask was replaced with nitrogen. Then,tetrahydrofuran (25 mL) was added to dissolve [RuClH(PPh₃)₃] and L^(1a).After 1 hour of heating under reflux, most of the tetrahydrofuran wascollected under reduced pressure. Thereafter, hexane (25 mL) was added,and a crystal was filtered and washed with hexane, tetrahydrofuran, anddiethyl ether. The resultant crystal was dried under reduced pressure,and a ruthenium complex 2 (743 mg) was obtained.

¹H NMR (300 MHz, C₆D₆):

-   δ=−15.92 (t, J=27.2 Hz, 1H), 3.31 (m, 2H), 3.96 (m, 2H), 6.88-8.20    (m, 30H)

³¹P NMR (121.5 MHz, C₆D₆):

-   δ=59.9 (d, J=22 Hz)

Under a stream of nitrogen, the ruthenium complex 2 (0.2 mmol) wassuspended in toluene (20 mL). A solution of sodium borohydride (5.4mmol) in ethanol (20 mL) was added, and the mixture was heated for 1hour under reflux, then air-cooled, and concentrated under reducedpressure. After that, toluene (20 mL) was added, and the mixture wasstirred for 30 minutes and celite-filtered. The celite was washed withtoluene (20 mL). Under reduced pressure, most of the toluene wascollected, and hexane (20 mL) was added. A deposited crystal wasfiltered. The crystal was washed with hexane, and thus a rutheniumcomplex 1 (80 mg) was obtained. The isomer ratio was 4:3 based on thearea ratio of the hydride on the ruthenium according to H NMR.

The signals of the hydride on the ruthenium were as follows.

¹H NMR (300 MHz, C₆D₆)

-   Major isomer; δ −15.13 (dd, J=21.9 Hz, 25.8 Hz)-   Minor isomer; δ −14.30 (t, J=26.1 Hz)

Meanwhile, the signals of ³¹PNMR were as follows.

³¹PNMR (121.5 MHz, C₆D₆)

-   Major isomer; δ 66.4 (d, J=32 Hz), 64.7 (d, J=32 Hz)-   Minor isomer; δ 65.4 (s)

The ruthenium complex 1 (0.0181 mmol) thus prepared was charged into a100-mL autoclave equipped with a stirrer, and air inside the autoclavewas replaced with nitrogen. Then, a solution of L-Boc-alanine methylester (3.16 mmol) in tetrahydrofuran (1.4 mL) was added thereinto. Then,the mixture was subjected to hydrogenation at a hydrogen pressure of 5MPa at 80° C. for 16.0 hours. The reaction liquid was analyzed by gaschromatography. As a result, 2-Boc-aminopropanol was synthesized at aconversion rate of 68.0% and a selectivity of 97.4%.

Example 2 Hydrogenation of Methyl Benzoate

Methyl benzoate (7.99 mmol), a ruthenium complex 1 (0.004 mmol), andtetrahydrofuran (6 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 15.5 hours. The reaction liquidwas analyzed by gas chromatography. As a result, benzyl alcohol wassynthesized at a conversion rate of 96.2% and a selectivity of 86.7%.

Example 3 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (2.46 mmol), a ruthenium complex 1 (0.005mmol), and tetrahydrofuran (1 mL) were charged into a 100-mL autoclaveequipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 80° C. for 15.5 hours.The reaction liquid was analyzed by gas chromatography. As a result,2-Boc-aminopropanol was synthesized at a conversion rate of 38.0% and aselectivity of 95.3%. The obtained alcohol had an optical purity of98.8% ee.

Example 4 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (2.46 mmol), a ruthenium complex 1 (0.005mmol), and tetrahydrofuran (1 mL) were charged into a 100-mL autoclaveequipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 100° C. for 16 hours.The reaction liquid was analyzed by gas chromatography. As a result,2-Boc-aminopropanol was synthesized at a conversion rate of 51.9% and aselectivity of 89.7%.

Example 5 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (2.46 mmol), a ruthenium complex 1 (0.005mmol), and tetrahydrofuran (1 mL) were charged into a 100-mL autoclaveequipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 120° C. for 8.0 hours.The reaction liquid was analyzed by gas chromatography. As a result,2-Boc-aminopropanol was synthesized at a conversion rate of 77.7% and aselectivity of 93.4%. The obtained alcohol had an optical purity of98.2% ee.

Example 6 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (5 mmol), a ruthenium complex 1 (0.025 mmol),and tetrahydrofuran (2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction solutionwas diluted with 20 mL of diethyl ether, and was passed through 10 g ofsilica gel. The silica gel was washed with diethyl ether. The solutionthus obtained was concentrated under reduced pressure. The residue waspurified by silica gel column chromatography (silica gel 15 g,hexane/ethyl acetate=2/1 to 1/1). Thus, 2-Boc-aminopropanol (739 mg,98.4% ee) was obtained.

Example 7 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (5 mmol), a ruthenium complex 1 (0.025 mmol),and tetrahydrofuran (2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 100° C. for 16 hours. The reactionsolution was diluted with 20 mL of diethyl ether, and was passed through10 g of silica gel. The silica gel was washed with diethyl ether. Thesolution thus obtained was concentrated under reduced pressure. Theresidue was purified by silica gel column chromatography (silica gel 15g, hexane/ethyl acetate=2/1 to 1/1). Thus, 2-Boc-aminopropanol (719 mg,98.0% ee) was obtained.

Example 8 Hydrogenation of Methyl (S)-2-methyl-3-phenylpropionate

Methyl (S)-2-methyl-3-phenylpropionate (5 mmol, 78.4% ee), a rutheniumcomplex 1 (0.01 mmol), and tetrahydrofuran (2 mL) were charged into a100-mL autoclave equipped with a stirrer. Then, the mixture wassubjected to hydrogenation at a hydrogen pressure of 5 MPa at 80° C. for16 hours. The reaction liquid was analyzed by gas chromatography. As aresult, (S)-2-methyl-3-phenylpropanol was obtained at a conversion rateof 99.0% and a selectivity of 98.6%. The obtained alcohol had an opticalpurity of 77.9% ee.

Example 9 Hydrogenation of Methyl (R)-3-aminobutanoate

A ruthenium complex 1 (0.333 mmol) was charged into a 100-mL autoclaveequipped with a stirrer, and air inside the autoclave was replaced withnitrogen. Tetrahydrofuran (40 mL) and methyl (R)-3-aminobutanoate (100mmol, 99% ee or more) were charged thereinto. Then, the mixture wassubjected to hydrogenation at a hydrogen pressure of 3.5 MPa to 5 MPa at80° C. for 14 hours. The reaction liquid was concentrated, and theobtained residue was distilled. Thus, (R)-3-aminobutanol (7.39 g;boiling point of 84 to 86° C./14 Torr) was obtained. The obtainedalcohol had an optical purity of 99% ee or more.

Example 10 Hydrogenation of Methyl 3-dimethylaminopropionate

Methyl 3-dimethylaminopropionate (5 mmol), a ruthenium complex 1 (0.05mmol), and tetrahydrofuran (2 mL) were charged into a 100-mL autoclaveequipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 80° C. for 16 hours.The reaction liquid was analyzed by gas chromatography. As a result,3-dimethylaminopropanol was obtained at a conversion rate of 100% and aselectivity of 97.5%.

Example 11 Hydrogenation of Phthalide

Phthalide (5 mmol), a ruthenium complex 1 (0.025 mmol), andtetrahydrofuran (2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 100° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, 1,2-benzenedimethanolwas obtained at a conversion rate of 66% and a selectivity of 99% ormore.

Example 12 Hydrogenation of Methyl Nicotinate

Methyl nicotinate (8 mmol), a ruthenium complex 1 (0.008 mmol), andtetrahydrofuran (3.2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, 3-pyridinemethanol wasobtained at a conversion rate of 42% and a selectivity of 99% or more.

Example 13 Hydrogenation of Benzyl Benzoate

Benzyl benzoate (8 mmol), a ruthenium complex 1 (0.008 mmol), andtetrahydrofuran (3.2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, benzyl alcohol wasobtained at a conversion rate of 23% and a selectivity of 98%.

Example 14 Hydrogenation of Methyl 2-furoate

Methyl 2-furoate (8 mmol), a ruthenium complex 1 (0.016 mmol), andtetrahydrofuran (3.2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, furfuryl alcohol wasobtained at a conversion rate of 33% and a selectivity of 99% or more.

Example 15 Hydrogenation of Dimethyl Succinate

Dimethyl succinate (8 mmol), a ruthenium complex 1 (0.016 mmol), andtetrahydrofuran (3.2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, 1.4-butanediol wasobtained at a conversion rate of 50% and a selectivity of 71%.

Example 16 Hydrogenation of Methyl (R)-2-hydroxypropionate

A ruthenium complex 1 (0.125 mmol) was charged into a 100-mL autoclaveequipped with a stirrer, and air inside the autoclave was replaced withnitrogen. Tetrahydrofuran (40 ml) and methyl (R)-2-hydroxypropionate (25mmol, 99.3% ee) were added thereinto. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 4.6 MPa to 5 MPa at 80° C. for 5hours. The reaction liquid was analyzed by gas chromatography. As aresult, (R)-1,2-propanediol was obtained at a conversion rate of 98.6%and a selectivity of 98.4%. The obtained alcohol had an optical purityof 96.6% ee.

Example 17 Synthesis of Ruthenium Complex 3

[RuClH(PPh₃)₃] (1.22 mmol) and L^(3a) (2.44 mmol) were charged into a100 ml-flask, and air inside the flask was replaced with nitrogen. Then,toluene (15 ml) was added to dissolve [RuClH(PPh₃)₃] and L^(3a). After 1hour and 30 minutes of heating at 70° C. and then 30 minutes of coolingin an ice bath, a deposited crystal was filtered under nitrogenatmosphere, and washed with diethyl ether. The resultant crystal wasdried under reduced pressure, and a ruthenium complex 4 (790 mg) wasobtained. The isomer ratio was 2:1 based on the area ratio of thehydride on the ruthenium according to ¹H NMR.

The signals of the hydride on the ruthenium were as follows.

¹H NMR (300 MHz, CD₂Cl₂):

-   Major isomer; δ −19.79 (t, J=28.2 Hz)-   Minor isomer; δ −19.58 (dd, J=24.9 Hz, 30.0 Hz)

³¹P NMR (121.5 MHz, CD₂Cl₂):

-   Major isomer; δ 75.48 (d, J=24.7 Hz)-   Minor isomer; δ 77.1 (d, J=36.2 Hz), 73.2 (d, J=36.2 Hz)

Under a stream of nitrogen, the ruthenium complex 4 (0.7 mmol) wassuspended in toluene (15 ml). A solution of sodium borohydride (11.1mmol) in ethanol (15 ml) was added, and the mixture was heated at 70° C.for 15 minutes, and then stirred at room temperature for 1 hour,air-cooled, and concentrated under reduced pressure. After that, toluene(30 ml) was added, and the mixture was stirred for 20 minutes andcelite-filtered. The celite was washed with toluene (10 ml). Underreduced pressure, most of the toluene was collected, and hexane (10 ml)was added. A deposited crystal was filtered. The crystal was washed withdiethyl ether, and thus a ruthenium complex 3 (390 mg) was obtained.

¹H NMR (300 MHz, CD₂Cl₂):

-   δ=−15.70 (t, J=26.7 Hz, 1H), −1.8 (br, 4H), 2.25 (m, 2H), 2.39 (m,    2H), 2.65 (m, 2H), 2.92 (m, 2H), 3.86 (t, J=12.3 Hz, 2H), 4.16-4.52    (m, 4H), 6.87-7.50 (m, 30H)

³¹P NMR (121.5 MHz, CD₂Cl₂):

-   δ=77.4

Example 18 Synthesis of Ruthenium Complex 3

[RuCl₂(PPh₃)₃] (0.75 mmol) and L^(4a) (1.58 mmol) were charged into a100 ml-flask, and air inside the flask was replaced with nitrogen. Then,toluene (5 ml) was added to dissolve [RuCl₂(PPh₃)₃] and L^(4a). After 40minutes of heating at 80° C. and then cooling to room temperature, adeposited crystal was filtered under nitrogen atmosphere, and washedwith toluene and diethyl ether. The resultant crystal was dried underreduced pressure, and a ruthenium complex 5 (450 mg) was obtained.

¹H NMR (300 MHz, C₆D₆):

-   δ=2.50 (m, 4H), 4.72 (m, 4H), 6.90-7.10 (m, 22H), 7.48-7.54 (m, 8H),    9.22 (S, 2H)

³¹P NMR (121.5 MHz, C₆D₆):

-   δ=55.9

Under a stream of nitrogen, the ruthenium complex 5 (0.12 mmol) wasdissolved in toluene (4 ml). A solution of sodium borohydride (1.3 mmol)in ethanol (4 ml) was added, and the mixture was heated at 80° C. for 1hour. Then, sodium borohydride (1.3 mmol) was added, and the mixture washeated at 80° C. for 1 hour. Sodium borohydride (1.3 mmol) was furtheradded, and stirred at 80° C. for 10 minutes and subsequently at roomtemperature for 30 minutes, then air-cooled, and concentrated underreduced pressure. After that, toluene (10 ml) was added, and the mixturewas stirred for 30 minutes and celite-filtered. Under reduced pressure,most of the toluene was collected, and heptane (3 ml) was added. Adeposited crystal was filtered under nitrogen atmosphere. The crystalwas washed with heptane, and thus a ruthenium complex 3 (20 mg) wasobtained.

¹H NMR (300 MHz, CD₂Cl₂):

-   δ=−15.70 (t, J=26.7 Hz, 1H), −1.8 (br, 4H), 2.25 (m, 2H), 2.39 (m,    2H), 2.65 (m, 2H), 2.92 (m, 2H), 3.86 (t, J=12.3 Hz, 2H), 4.16-4.52    (m, 4H), 6.87-7.50 (m, 30H)

³¹P NMR (121.5 MHz, CD₂Cl₂):

-   δ=77.4

Example 19 Hydrogenation of Methyl Benzoate

Methyl benzoate (8 mmol), a ruthenium complex 3 (0.008 mmol), andtetrahydrofuran (4 ml) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, benzyl alcohol wasobtained at a conversion rate of 100% and a selectivity of 99.1%.

Example 20 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (5 mmol), a ruthenium complex 3 (0.01 mmol),and tetrahydrofuran (2 ml) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, 2-Boc-aminopropanol wassynthesized at a conversion rate of 77.9% and a selectivity of 80.3%.The obtained alcohol had an optical purity of 99.3% ee.

Example 21 Hydrogenation of Methyl (R)-3-hydroxybutanoate

Methyl (R)-3-hydroxybutanoate (5 mmol, 98.9% ee), a ruthenium complex 3(0.05 mmol), and tetrahydrofuran (2 ml) were charged into a 100-mLautoclave equipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 80° C. for 16 hours.The reaction liquid was analyzed by gas chromatography. As a result,(R)-1,3-butanediol was obtained at a conversion rate of 57.8% and aselectivity of 95.0%. The obtained alcohol had an optical purity of98.9% ee.

Example 22 Synthesis of Ruthenium Complex 6

[RuCl₂(PPh₃)₃] (0.93 mmol) and L^(6a) (1.86 mmol) were charged into a100 ml-flask, and air inside the flask was replaced with nitrogen. Then,toluene (10 ml) was added to dissolve [RuCl₂(PPh₃)₃] and L^(6a). After 1hour and 30 minutes of heating at 100° C., most of toluene was collectedunder reduced pressure, and hexane (6 ml) was added. A deposited crystalwas filtered under nitrogen atmosphere. The resultant crystal was driedunder reduced pressure, and a ruthenium complex 7 (578 mg) was obtained.

³¹P NMR (121.5 MHz C₆D₆):

-   δ 53.5

Under a stream of nitrogen, the ruthenium complex 7 (0.81 mmol) wasdissolved in toluene (9 ml). A solution of sodium borohydride (12.2mmol) in ethanol (9 ml) was added, and the mixture was heated at 70° C.for 30 minutes, then stirred at room temperature for 30 minutes,air-cooled, and concentrated under reduced pressure. After that, toluene(18 ml) was added, and the mixture was stirred for 20 minutes andcelite-filtered. The celite was washed with toluene (2 ml). Underreduced pressure, most of the toluene was collected, and hexane (4 ml)was added. A deposited crystal was filtered under nitrogen atmosphere.The crystal was washed with diethyl ether, and thus a ruthenium complex6 (348 mg) was obtained.

¹H NMR (300 MHz, C₆D₆):

-   δ=−15.26 (dd, J=23.4 Hz, J=26.7 Hz, 1H), −1.1 (br, 4H), 1.02-1.11    (m, 1H), 1.28-1.63 (m, 7H), 2.12-2.55 (m, 6H), 2.98-3.14 (m, 3H),    3.43-3.51 (m, 1H), 4.41 (br, 1H), 4.88-4.99 (m, 1H), 6.88-7.17 (m,    12H), 7.32-7.39 (m, 2H), 7.46-7.52 (m, 2H), 7.60-7.70 (m, 4H)

³¹P NMR (121.5 MHz, C₆D₆):

-   δ=74.5 (d, J=34.5 Hz), 79.7 (d, J=34.5 Hz)

Example 23 Hydrogenation of L-Boc-alanine Methyl Ester

L-Boc-alanine methyl ester (5 mmol), a ruthenium complex 6 (0.05 mmol),and tetrahydrofuran (2 ml) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction liquidwas analyzed by gas chromatography. As a result, 2-Boc-aminopropanol wassynthesized at a conversion rate of 99.8% and a selectivity of 98.3%.The obtained alcohol had an optical purity of 98.6% ee.

Comparative Example 1 Hydrogenation of L-Boc-Alanine Methyl Ester UnderCondition that Dichlororuthenium Complex 8 was used without Adding Base

L-Boc-alanine methyl ester (5.0 mmol), a dichlororuthenium complex 8(0.05 mmol), and tetrahydrofuran (2 ml) were charged into a 100-mLautoclave equipped with a stirrer. Then, the mixture was subjected tohydrogenation at a hydrogen pressure of 5 MPa at 80° C. for 18.0 hours.The reaction liquid was analyzed by gas chromatography. As a result, noalcohol was observed, and the raw material, i.e., the ester, remained.

Comparative Example 2 Hydrogenation of L-Boc-Alanine Methyl Ester UnderCondition that Dichlororuthenium Complex 8 was Used with Adding Base

L-Boc-alanine methyl ester (5.0 mmol), sodium methoxide (5 mmol), adichlororuthenium complex 8 (0.05 mmol), and tetrahydrofuran (2 mL) werecharged into a 100-mL autoclave equipped with a stirrer. Then, themixture was subjected to hydrogenation at a hydrogen pressure of 5 MPaat 80° C. for 18.0 hours. The reaction solution was diluted with 5 mL ofmethanol and 20 mL of diethyl ether, and purified with 10.0 g of silicagel (diethyl ether/methanol=10/1). A racemic body of4-methyl-2-oxazolidinone (356 mg) was obtained.

Comparative Example 3 Hydrogenation of Methyl(S)-2-Methyl-3-Phenylpropionate Under Condition that DichlororutheniumComplex 8 was Used without Adding Base

Methyl (S)-2-methyl-3-phenylpropionate (5 mmol, 78.4% ee), adichlororuthenium complex 8 (0.05 mmol), and tetrahydrofuran (2 mL) werecharged into a 100-mL autoclave equipped with a stirrer. Then, themixture was subjected to hydrogenation at a hydrogen pressure of 5 MPaat 80° C. for 16 hours. The reaction liquid was analyzed by gaschromatography. As a result, no alcohol was observed, and the rawmaterial, i.e., the ester, remained.

Comparative Example 4 Hydrogenation of Methyl(S)-2-methyl-3-Phenylpropionate Under Condition that DichlororutheniumComplex 8 was Used with Adding Base

Methyl (S)-2-methyl-3-phenylpropionate (5 mmol, 78.4% ee), adichlororuthenium complex 8 (0.05 mmol), sodium methoxide (5 mmol), andtetrahydrofuran (2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction solutionwas diluted with 20 mL of diethyl ether, and was passed through 8.9 g ofsilica gel. The silica gel was washed with diethyl ether. The solutionthus obtained was concentrated under reduced pressure. The residue waspurified by silica gel column chromatography (silica gel 13.4 g,hexane/ethyl acetate=8/1). Thus, (S)-2-methyl-3-phenylpropanol (645 mg,18.4% ee) was obtained.

Comparative Example 5 Hydrogenation of L-Boc-Alanine Methyl Ester withAdding Base

L-Boc-alanine methyl ester (5 mmol), sodium methoxide (5 mmol), aruthenium complex 1 (0.025 mmol), and tetrahydrofuran (2 mL) werecharged into a 100-mL autoclave equipped with a stirrer. Then, themixture was subjected to hydrogenation at a hydrogen pressure of 5 MPaat 100° C. for 16 hours. The reaction solution was diluted with 5 mL ofmethanol and 20 mL of diethyl ether, and was passed through 10.0 g ofsilica gel. The silica gel was washed with diethyl ether. The solutionthus obtained was concentrated under reduced pressure. The residue waspurified by silica gel column chromatography (silica gel 15.0 g,hexane/ethyl acetate=1/2). A racemic body of 4-methyl-2-oxazolidinone(322 mg) was obtained.

Comparative Example 6 Hydrogenation of Methyl(S)-2-methyl-3-Phenylpropionate with Adding Base

Methyl (S)-2-methyl-3-phenylpropionate (5 mmol, 78.4% ee), sodiummethoxide (1 mmol), a ruthenium complex 1 (0.01 mmol), andtetrahydrofuran (2 mL) were charged into a 100-mL autoclave equippedwith a stirrer. Then, the mixture was subjected to hydrogenation at ahydrogen pressure of 5 MPa at 80° C. for 16 hours. The reaction solutionwas diluted with 20 mL of diethyl ether, and was passed through 8.9 g ofsilica gel. The silica gel was washed with diethyl ether. The obtainedsolution was concentrated under reduced pressure. The residue waspurified by silica gel column chromatography (silica gel 13.4 g,hexane/ethyl acetate=8/1). (S)-2-Methyl-3-phenylpropanol (657 mg, 1% ee)was obtained.

Comparative Example 7 Hydrogenation of Methyl (R)-3-Aminobutanoate withAdding Base

Methyl (R)-3-aminobutanoate (5 mmol), sodium methoxide (1 mmol), aruthenium complex 1 (0.05 mmol), and tetrahydrofuran (2 mL) were chargedinto a 100-mL autoclave equipped with a stirrer. Then, the mixture wassubjected to hydrogenation at a hydrogen pressure of 5 MPa at 80° C. for16 hours. The reaction liquid was analyzed by gas chromatography. As aresult, the reaction gave a complicated mixture, and the raw materialdisappeared; however, a targeted alcohol was not synthesized.

What is claimed is:
 1. A method for producing an alcohol, the methodcomprising the step of reducing an ester or a lactone with hydrogen toproduce a corresponding alcohol without addition of a base compound inthe presence of, as a catalyst, a ruthenium complex represented by thefollowing general formula (1):RuH(X)(L¹)(L²)  (1) wherein X represents BH₄, L¹ and L² each represent abidentate ligand represented by the following general formula (3):

wherein R⁷, R⁸, R⁹, R¹⁰ and R¹¹, which may be same or different, eachrepresent a hydrogen atom, an alkyl group which may have a substituent,an aryl group which may have a substituent, an aralkyl group which mayhave a substituent, or a cycloalkyl group which may have a substituent,R⁷ and R⁸, R⁷ and R⁹, R⁸ and R⁹, or R¹⁰ and R¹¹ may bond to each otherto form a ring, and Q³ represents a divalent arylene group which mayhave a substituent, an alkylene group which may have a substituent, or abond.
 2. The production method according to claim 1, wherein the complexis obtained by reducing a ruthenium complex including a bidentate ligandrepresented by the following general formulae (7a) or (7b):

wherein R²², R²³, R²⁴, R²⁵, R¹⁰⁰, R¹⁰¹, R¹⁰², R¹⁰³, R¹⁰⁴ and R¹⁰⁵, whichmay be same or different, each represent a hydrogen atom, an alkyl groupwhich may have a substituent, an aryl group which may have asubstituent, an aralkyl group which may have a substituent, or acycloalkyl group which may have a substituent, R²² and R²³, R²⁴ and R²⁵,or R¹⁰⁴ and R¹⁰⁵ may bond to each other to form a ring, and Q^(7a) andQ^(7b) each represent a divalent arylene group which may have asubstituent, an alkylene group which may have a substituent, or a bond,the ruthenium complex being represented by a general formula (6′):[Ru(X³)(X⁴)(L^(1″))(L^(2″))]  (6′) wherein X³ and X⁴ each independentlyrepresent a hydrogen atom or halogen atom, and L^(1″)and L^(2″), whichmay be same or different, each represent the bidentate ligandrepresented by the general formula (7a) or (7b).
 3. The productionmethod according to claim 1, wherein the prepared complex is used as thecatalyst without being isolated from a complex preparing solution. 4.The production method according to claim 1, wherein the ester or thelactone is an optically active substance, and the obtained alcohol holdsan optical purity of 90% or more of that of the ester or lactone reducedwith hydrogen.
 5. The production method according to claim 2, whereinthe prepared complex is used as the catalyst without being isolated froma complex preparing solution.